The present invention relates to a storage and order-picking system. Further, the present invention relates to a method of storing and retrieving articles in a sequenced manner into and from a rack arrangement for providing the articles in a sequenced manner, for example, in an ascending order, and in an order-orientated manner, for example, at a target location (e.g., picking-work station). For this purpose in particular a driverless, or operatorless, transport system (FTS) having autonomous driverless transport vehicles (FTF) is used. Classic pre-zone, which is characterized by steady conveyors, is replaced by an FTF plane. Particularly, the invention is used in “case-picking” scenarios.
The present invention further relates a system for loading and unloading a piece good, or an article, on and from an FTF.
RELATED PRIOR ART With both “case picking” and “piece picking” storage containers are transported in an order-orientated manner from a warehouse towards a picking-work station for the purpose of article removal and delivery. The warehouse comprises racks in which the articles can be stored with or without load supports. The storage and retrieval of the articles is performed by means of storage and retrieval devices, load-handling devices (LHD) of which are typically moveable horizontally and, if necessary, vertically in rack aisles being defined between the racks. The storage and retrieval devices are supplied with the articles via vertical conveyors, or elevators, which in turn are arranged at a front face of the racks and rack aisles. A corresponding arrangement is exemplarily disclosed in the document U.S. Pat. No. 7,261,509 B. The elevators convey the articles vertically to a conveying system plane being arranged adjacent again at a front face, or front end, of the racks and rack aisles. This conveying-line plane is also designated as a “pre-zone”.
Typically, the pre-zone comprises a plurality of conveying-line branches which are used as buffering lines for connecting the respective rack aisles in a conveying manner to a sorting circle which brings the retrieved articles into a desired order, i.e. the articles are delivered in the desired order to one or more target locations (e.g., picking-work station). The document US 2010/300048 A1 discloses a pre-zone having buffering lines between a centrally arranged sorting circle and elevators being arranged at a front face. Since the buffering lines and the sorting circle respectively comprise an unchangeable course of lines and since the sorting circle has a limited receiving capacity it is required that the storage and retrieval devices and the elevators, which represent two separate sequencing stages, sequence the articles in advance. This means that the storage and retrieval devices retrieve the articles in a predetermined order (first sequencing stage) which corresponds roughly, but not exactly, to the desired order. If several storage and retrieval devices are operated on top of each other a (rack) plane, from which the elevators retrieve the articles being delivered by the storage and retrieval devices in order to transport the articles vertically towards the pre-zone, represents a further second sequencing stage. In a third sequencing stage (sorting circle) the final sequencing is performed in terms of delivery to the target location(s). In this case planning and controlling efforts are significant for bringing the articles in the desired order to the work station (target location). The planning needs to be performed in advance in three stages and already starts with the selection of one of the storage and retrieval devices. Then the storage and retrieval devices need to cover, due to the sequence, very long ways, or paths, within the rack aisles for retrieving an article preset by the (pre-) sequence and for bringing same to the elevator arranged at the front face.
Another problem is to be seen in the space available to the system. The pre-zone is arranged, as a rule, in front of the warehouse at the front face. Typically the pre-zone is relatively small (compared to the warehouse). The steady conveyors (such as roller lines, belt conveyors, strap conveyors, chain conveyors, etc.), which are used in the pre-zone, have a fixed course of lines which cannot be changed simply. After start-up of the system the course of lines, particularly within the pre-zone, is actually preset in a fixed manner and unchangeable. The conveying components of the pre-zone often are difficult to access just because of the spare space for maintenance operations. In FIG. 1 of the document DE 101 36 354 A1 it is disclosed a relatively complex course of lines of the conveying system within the pre-zone for supplying two work stations with storage containers via two separate conveying circles. As a rule, the pre-zone is crossed by an additional conveying line dedicated to order containers so that even less space is available.
A “steady conveyor” is to be understood as conveyor which transports the conveying goods (bulk material or piece goods) in a steady flow from one or more deposition locations (sources) to one or more delivery locations (targets). Examples of steady conveyors are: belt conveyors, roller conveyors, chain conveyors, and circle conveyors. Typical features of steady conveyors are: continuous/discrete-continuous conveying-good stream, central drive in continuous operation, loading and unloading in operation, always ready for receiving/delivering, and stationary devices. The continuous operation allows transport of relatively huge amounts in short time (compared to non-steady conveyors).
A front-face transfer of the articles from and into the racks via the elevators, which are arranged at the front face, represents a bottle neck of performance. Performance is to be understood in the following as a number of storage/retrieval processes per unit of time, or a number of picks per unit of time. In the document WO 2007/134840 A, which has been filed on behalf of the applicant, it is disclosed a warehouse layout which deviates from the arrangement of the elevators at the front face. WO 2007/134840 A proposes to respectively position a plurality of elevators laterally to the longitudinal sides of the racks for increasing—compared to elevators arranged at the front face—the performance. However, this plurality of elevators is in turn coupled to conventional steady conveyors which bring the retrieved articles to (picking) work stations which are located, as a rule, far away. Due to the utilization of steady conveyors in the pre-zone WO 2007/134840 A still requires pre-sequencing by means of the storage and retrieval devices within the warehouse, or within the racks. Additionally, the steady conveyors require relatively much space and thus make, amongst other things, a spatial compaction of the warehouse layout difficult.
A different conceptual approach is described in the document EP 2 044 494 A1. There, autonomous vehicles (shuttles) are disclosed which move smallest racks within an action area from a storage region into a picking region. This means that to-be-picked articles are not retrieved from the racks and are not transported to the work stations by means of the vehicles, but that the vehicles transport the racks directly to the work stations. However, even in this case planning efforts are significant. The sequencing is complicated because entire racks need to be moved in the right order (and orientation) to the work station.
The document DE 10 2008 039 764 A1 discloses driverless transport vehicles having comb-prong-like deposition webs, which are attached to a top side and on which goods are transported. This comb-prong-like webs mesh with horizontally arranged rollers of a roller track, which rollers are distanced to each other and mesh the goods from the webs or deliver the goods to the webs. The goods are fed and discharged perpendicularly to a travelling direction of the transport vehicle. The vehicle can drive continuously through the rollers of the roller track during transfer. However, in any case stoppers are required for holding the goods during the transfer. For unloading the vehicle a static stopper is sufficient. For loading the vehicle moveable stoppers are required.
During unloading of the vehicles relatively much time is required since the delivered goods need to be discharged first laterally via the roller track before a subsequent vehicle can deliver its goods to the roller track. Loading process is similar. A subsequent vehicle can only be loaded if the vehicle, which drives ahead, has received its good completely. This means that during both unloading and loading distances need to be maintained, or are generated gaps between subsequent goods or vehicles. Thus, the loading and unloading cannot happen in terms of a continuous stream where the goods follow each, or flow, directly without distances.
During loading of the vehicles the stopper needs to be moved since the stopper first needs to hold the to-be-delivered good and then release same. For the movement of the stopper mechanical links, or controlled actuators, are required. Actuators need to be controlled so that a corresponding controlling device is required.